The Skin Microbiome in Inflammatory Skin Diseases

Purpose of Review: Ongoing investigations of the human skin microbiome strongly suggest a connection to skin diseases and skin health. This review provides an overview of recent literature on the skin microbiome in relation to skin diseases, with a specific focus on common inflammatory skin conditions, such as atopic dermatitis, psoriasis, hidradenitis suppurativa, acne, and rosacea. Recent Findings: In healthy subjects, the skin microbiome mediates fundamental processes involving the immune response and epidermal development and differentiation. Microbiome characteristics in inflammatory skin diseases differ depending on disease, as both topography and disease severity and even host genetics seem to influence the microbiome composition. Not only the bacterial species are important but also different strains within the same species can act differently, where some can be commensal and protect against microbial dysbiosis, whereas others can induce skin inflammation and immune reactions in humans. Summary: The interplay between skin microbes, host genetics, and the immune system is anticipated to be of importance for both the development and severity of many skin diseases. However, the causality of specific pathogens and the effect on the pathogenesis in relation to inflammatory skin diseases is yet to be understood.